An assessment of the immunosuppressive activity of the anti-tumour compound 4′-[(9-acridinyl)amino]methanesulphon-m-anisidide (m-AMSA)

Abstract

The experimental anti-tumour compound 4′-[( 9-acridinyl)-amino] methanesulphon-m-anisidide (m-AMSA, NSC 156303), which is highly active against experimental tumours, suppressed the direct plaque-forming cell (PFC) response to sheep red blood cells in mice. The maximum tolerated dose had no effect on the PFC response when injected before or up to 12 hr after injection of antigen, yet it suppressed the response by 99·5% when injected 28 hr after the antigen. A more complete assessment of the suppression by this agent was gained by using spleen cell transfer and spleen cell culture systems. Mice pre-treated with cyclophosphamide ( 120 mg/kg) which behave as B-cell deficient animals, were used as recipients for cell transfer. Treatment of either the donor mouse or donor spleen cells with m-AMSA showed that B cells changed from a drug-insensitive to a drug-sensitive state between 4 and 27 hr after contact with antigen. Similar deductions could be made from experiments where the PFC response was measured in cultured spleen cells which were pre-treated with the drug m-AMSA may be useful to distinguish different developmental stages of the precursors of PFC.